Fast Parabolic Approximations for Acoustic Propagation in the Atmosphere PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Fast Parabolic Approximations for Acoustic Propagation in the Atmosphere PDF full book. Access full book title Fast Parabolic Approximations for Acoustic Propagation in the Atmosphere by . Download full books in PDF and EPUB format.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 68
Get Book Here
Book Description
Parabolic equations can be used to find approximate solutions to the reduced wave equation. By reducing the equation to first order in the range derivative, the solution can be found by marching forward in range. Several numerical techniques can be applied to the solution of the parabolic equation (PE), including finite elements, finite differences, and a Fourier Transform method known as the split-step PE. The split-step solves for each range increment in two steps. First, it propagates forward through a homogenous atmosphere, using the Fourier Transform. It then applies a multiplicative phase correction for index-of-refraction variations. The split-step method leads to a computationally fast model for two reasons: the range steps are several wavelengths, and the Fourier Transform can be evaluated by a Fast Fourier Transform. One of the difficulties encountered in applying the split-step PE to outdoor sound propagation is accommodation of the complex ground impedance. The Green's function PE is a split-step PE which solves for the one-dimensional height-dependant Green's function in a homogenous atmosphere. This Green's function incorporates the complex ground impedance as a complex, angle-dependant plane-wave reflection coefficient. (AN).
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 68
Get Book Here
Book Description
Parabolic equations can be used to find approximate solutions to the reduced wave equation. By reducing the equation to first order in the range derivative, the solution can be found by marching forward in range. Several numerical techniques can be applied to the solution of the parabolic equation (PE), including finite elements, finite differences, and a Fourier Transform method known as the split-step PE. The split-step solves for each range increment in two steps. First, it propagates forward through a homogenous atmosphere, using the Fourier Transform. It then applies a multiplicative phase correction for index-of-refraction variations. The split-step method leads to a computationally fast model for two reasons: the range steps are several wavelengths, and the Fourier Transform can be evaluated by a Fast Fourier Transform. One of the difficulties encountered in applying the split-step PE to outdoor sound propagation is accommodation of the complex ground impedance. The Green's function PE is a split-step PE which solves for the one-dimensional height-dependant Green's function in a homogenous atmosphere. This Green's function incorporates the complex ground impedance as a complex, angle-dependant plane-wave reflection coefficient. (AN).
Author: Vladimir E. Ostashev
Publisher:
ISBN:
Category : Differential equations, Partial
Languages : en
Pages : 16
Get Book Here
Book Description
The narrow-angle parabolic equation (NAPE) with the effective sound speed approximation (ESSA) is widely used for sound and infrasound propagation in a moving medium such as the atmosphere. However, it is valid only for angles less than 20° with respect to the nominal propagation direction. In this paper, the wave equation and extra-wide-angle parabolic equation (EWAPE) for high-frequency (short-wavelength) sound waves in a moving medium with arbitrary Mach numbers are derived without the ESSA. For relatively smooth variations in the medium velocity, the EWAPE is valid for propagation angles up to 90°. Using the Padé (n,n) series expansion and narrow-angle approximation, the EWAPE is reduced to the wide-angle parabolic equation (WAPE) and NAPE. Versions of these equations are then formulated for low Mach numbers, which is the case that is usually considered in the literature. The phase errors pertinent to the equations considered are studied. It is shown that the equations for low Mach numbers and the WAPE with the ESSA are applicable only under rather restrictive conditions on the medium velocity. An effective numerical implementation of the WAPE for arbitrary Mach numbers in the Padé (1,1) approximation is developed and applied to sound propagation in the atmosphere.
Author: E.M. Salomons
Publisher: Springer Science & Business Media
ISBN: 9781402003905
Category : Science
Languages : en
Pages : 352
Get Book Here
Book Description
Describes computational methods for sound propagation in the atmosphere. The book overviews models that take into account the presence of specific physical elements, then presents detailed mathematical descriptions of the models in a series of appendices. The models address sound propagation over a flat ground surface in a homogenous atmosphere and in a refracting atmosphere, and the effects of atmospheric turbulence, irregular terrain, and a noise barrier. The numerical methods include the generalized fast field program, the parabolic equation method, Green's function parabolic equations method, and a ray model. c. Book News Inc.
Author: Xunren Yang
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110383020
Category : Science
Languages : en
Pages : 462
Get Book Here
Book Description
This book concisely expounds the fundamental concepts, phenomena, theories and procedures in a complete and systematic sense. In this book, not only almost all the important achievements from predecessors but also the contributions from the author himself have been summed up profoundly. Starting from the derivation of fundamental equations, various classical acoustical phenomena such as reflection, refraction, scattering diffraction and absorption in atmosphere, as well as the influences of gravitation and rotation of the earth on the behaviors of different atmospheric waves including acoustic waves, have been discussed in viewpoints of wave acoustics and geometrical acoustics respectively. The recent developments of several computation methods in the field of atmospheric acoustics have been introduced in some detail. As for the application aspects, atmospheric remote sensing has been discussed from the angle of inverse problems.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722044244
Category :
Languages : en
Pages : 30
Get Book Here
Book Description
The effects of a ridge on a low-frequency acoustic propagation in quiescent and windy atmospheres are investigated using a parabolic approximation. A logarithmic wind-speed profile, commonly employed to model atmospheric wind currents, is modified and used to model two-dimensional atmospheric flow over a triangularly-shaped hill. The parabolic equation is solved using an implicit finite-difference algorithm. Several examples are examined to determine the combined effects of source-ridge distance, ridge dimensions, wind-speed profile, and CW source frequency on the received acoustic field. Robertson, J. S. and Jacobson, M. J. and Siegmann, W. L. and Santandrea, D. P. Unspecified Center NAG1-929...
Author: Gokhan Apaydin
Publisher: John Wiley & Sons
ISBN: 1119432138
Category : Science
Languages : en
Pages : 154
Get Book Here
Book Description
An important contribution to the literature that introduces powerful new methods for modeling and simulating radio wave propagation A thorough understanding of electromagnetic wave propagation is fundamental to the development of sophisticated communication and detection technologies. The powerful numerical methods described in this book represent a major step forward in our ability to accurately model electromagnetic wave propagation in order to establish and maintain reliable communication links, to detect targets in radar systems, and to maintain robust mobile phone and broadcasting networks. The first new book on guided wave propagation modeling and simulation to appear in nearly two decades, Radio Wave Propagation and Parabolic Equation Modeling addresses the fundamentals of electromagnetic wave propagation generally, with a specific focus on radio wave propagation through various media. The authors explore an array of new applications, and detail various virtual electromagnetic tools for solving several frequent electromagnetic propagation problems. All of the methods described are presented within the context of real-world scenarios typifying the differing effects of various environments on radio-wave propagation. This valuable text: Addresses groundwave and surface wave propagation Explains radar applications in terms of parabolic equation modeling and simulation approaches Introduces several simple and sophisticated MATLAB scripts Teaches applications that work with a wide range of electromagnetic, acoustic and optical wave propagation modeling Presents the material in a quick-reference format ideal for busy researchers and engineers Radio Wave Propagation and Parabolic Equation Modeling is a critical resource forelectrical, electronics, communication, and computer engineers working on industrial and military applications that rely on the directed propagation of radio waves. It is also a useful reference for advanced engineering students and academic researchers.
Author: E.M. Salomons
Publisher: Springer Science & Business Media
ISBN: 9401006601
Category : Science
Languages : en
Pages : 331
Get Book Here
Book Description
Noise from cars, trains, and aeroplanes can be heard at large distances from the source. Accurate predictions of the loudness of the noise require accurate computations of sound propagation in the atmosphere. This book describes models that can be used for these computations. The models take into account complex effects of the atmosphere and the ground surface on sound waves, including the effects of wind and temperature distributions, atmospheric turbulence, irregular terrain, and noise barriers. The main text of the book focuses on physical effects in atmospheric acoustics. The effects are illustrated by many numerical examples. The main text requires a very limited mathematical background from the reader; detailed mathematical descriptions of the models, developed from the basic principles of acoustics, are presented in appendices. Models for moving media are compared with models that are based on the effective sound speed approach. Both two-dimensional models and three-dimensional models are presented. As meteorological effects play an important role in atmospheric acoustics, selected topics from boundary layer meteorology and the theory of turbulence are also presented.
Author: Mireille Levy
Publisher: IET
ISBN: 9780852967645
Category : Mathematics
Languages : en
Pages : 360
Get Book Here
Book Description
Provides scientists and engineers with a tool for accurate assessment of diffraction and ducting on radio and radar systems. The author gives the mathematical background to parabolic equations modeling and describes simple parabolic equation algorithms before progressing to more advanced topics such as domain truncation, the treatment of impedance boundaries, and the implementation of very fast hybrid methods combining ray-tracing and parabolic equation techniques. The last three chapters are devoted to scattering problems, with application to propagation in urban environments and to radar-cross- section computation. Annotation copyrighted by Book News, Inc., Portland, OR
Author: Robert M. Manning
Publisher: BiblioGov
ISBN: 9781289264659
Category :
Languages : en
Pages : 40
Get Book Here
Book Description
The extended wide-angle parabolic wave equation applied to electromagnetic wave propagation in random media is considered. A general operator equation is derived which gives the statistical moments of an electric field of a propagating wave. This expression is used to obtain the first and second order moments of the wave field and solutions are found that transcend those which incorporate the full paraxial approximation at the outset. Although these equations can be applied to any propagation scenario that satisfies the conditions of application of the extended parabolic wave equation, the example of propagation through atmospheric turbulence is used. It is shown that in the case of atmospheric wave propagation and under the Markov approximation (i.e., the -correlation of the fluctuations in the direction of propagation), the usual parabolic equation in the paraxial approximation is accurate even at millimeter wavelengths. The methodology developed here can be applied to any qualifying situation involving random propagation through turbid or plasma environments that can be represented by a spectral density of permittivity fluctuations.
Author: Thomas Rossing
Publisher: Springer Science & Business Media
ISBN: 0387304460
Category : Science
Languages : en
Pages : 1179
Get Book Here
Book Description
This is an unparalleled modern handbook reflecting the richly interdisciplinary nature of acoustics edited by an acknowledged master in the field. The handbook reviews the most important areas of the subject, with emphasis on current research. The authors of the various chapters are all experts in their fields. Each chapter is richly illustrated with figures and tables. The latest research and applications are incorporated throughout, including computer recognition and synthesis of speech, physiological acoustics, diagnostic imaging and therapeutic applications and acoustical oceanography. An accompanying CD-ROM contains audio and video files.
